02 sensor...
 

any one know off hand if there is an O2 sensor after the cat on a 94 ls

nope. OBD1 has only one O2 sensor.... pre-cat.

good, i thought i was blind for awhile.

but can you move the sensor there from the header?

You can place it anywhere before the cat

but not in the cat.

I wouldnt. Flow is more restricted in the cat, therefore the sensor reading will be jacked up....

true, but what if it was reloacated to the front of the cat.

me and a friend are custom fabing up a header and cat.

only 1 sensor for the pre-96 ones. keep it where it's at

Mine is about 2 inches past the midshaft... but I dont have a cat. I wouldnt mount it too close before the cat. Gas stream slows down in that area due to restriction caused by the cat. At least mount it before it passes the firewall. That is the best area to allow for wiring route anyway.....